Olivenhain to start desalinating groundwater with test well

Construction starts this month on a $1.5 million test well to show whether desalinated groundwater could supplement the drinking water supply for 86,000 customers of the Olivenhain Municipal Water District.

The district serves parts of Encinitas, Carlsbad, San Diego, San Marcos, Solana Beach and neighboring communities, and relies almost entirely on water imported from the Colorado River and Northern California. Like agencies throughout Southern California, it’s looking for ways to diversify its water supply.

Drilling will begin in about two weeks on a 120-foot-deep well in the San Dieguito River watershed, water district officials said. Beginning around May, the well will be pumped for a year or longer at different rates to determine its effects on the water levels and quality in nearby existing wells on private property within the aquifer.

The district would have to produce at least 1 million gallons of water per day for the project to work, which probably would require a minimum of two wells.

Feasibility studies show the project could be cost-competitive with other water sources and that it would have no negative effects on other wells or the environment, district General Manager Joey Randall said in a recent presentation to the Del Mar City Council.

Groundwater was pumped heavily for agricultural irrigation through the 1970s in the area and some of those wells remain in use, Randall said.

Construction of the complete desalinization project, should the pilot well prove successful, would cost about $30 million, he said. That would include the wells, water filtration equipment and pipes linking to the water supply and for the concentrated brine removal. Most of the money is expected to come from government grants.

Groundwater desalinization is rare in Southern California, but the Oceanside municipal water district has been doing it for 20 years.

Oceanside announced earlier this year it will receive a $2.6 million grant to add two more wells, that will bring the city’s total to 10, all in the Mission Basin aquifer near the city’s airport along the San Luis Rey River.

With the additional wells, the city expects to get about 15 percent of its water from the Mission Basin aquifer.

Pushed by the increasing cost of imported water, agencies throughout the region also are increasing their reliance on recycled water.

—Phil Diehl is a reporter for The San Diego Union-Tribune

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